This invention relates to an apparatus for withdrawing bags from a vertically oriented bag forming element of a bag making machine and positioning the bags in compartments of an intermittently advanced conveyor. The bags are formed from a web of indeterminate length and have longitudinal and transverse seams. The apparatus has periodically opening and closing tongs for grasping each bag at least at one bag fold. The tongs are coupled with a drive for advancing and then withdrawing the tongs through the respective compartment of the conveyor.
U.S. Pat. No. 4,215,520 discloses a machine which makes bags from a web of indeterminate length on a forming element by providing successive longitudinal and transverse seams of the foil material. The bags are filled with the intended contents either directly through a hollow mandrel or are first formed on a solid mandrel and then advanced to a filling station. In either instance the conveyor has to be moved intermittently as conditioned by the timed, stepwise bag making method. The pauses in the process are necessitated by the time periods required for making the transverse seam, for the filling of the bags and further, for grasping each bag by the tongs and depositing the bag in the compartment then aligned with the tongs. The compartments may be constituted, according to the abovenoted U.S. patent, by containers supported on a conveyor belt or they may be formed by a space defined directly by chain elements of the conveyor.
It will be readily appreciated that the components which have to travel the longest path are the tongs and it is therefore the displacement of the tongs which requires the greatest share of the pauses in the process. For this reason the elements associated with this operation have to be submitted to large accelerations (and decelerations) in order to maintain the pauses as short as possible.